How to create realistic plastic effect in packaging
For the following cloth simulation, the ground plane is set to be a collision object and the box has the 'leather' cloth preset applied.

There is a Sub-Division modifier in the stack below the Cloth Sim modifier, you can place the Sub-D higher up the stack for more detail however this greatly increases the time needed for the calculations to run.

Once the simulation is run, you should have a series of frames to choose from.  Select the one you prefer and Apply the modifier so that the mesh becomes frozen in that shape.